3) Monodepth2+GT-ICP acquires a depth map with absolute scale in the same way as Monodepth2+USIP. However, it uses Iterative Closest Point (ICP) [1]}, [2]} to estimate the pose between the depth map and point cloud. Note that ICP fails without proper initialization, and thus we use the ground truth (GT) relative pose for initialization. Table REF  shows that our DeepI2P achieves similar RTE and better RRE compared to Monodepth2+GT-ICP, despite the latter has the unfair advantages of ground truth initialization and the depth map is perfectly calibrated.
